Handheld power tool with air-guiding element

ABSTRACT

A handheld power tool, including a housing wall and a fan device with an air intake and an air outlet in the housing wall. The fan device has an air guide, and an outflow space is delimited between, on the one hand, the housing wall at the air outlet and, on the other hand, an outflow side of the air intake, as well as laterally by a first surface contour and by a second surface contour of the air guide. The first surface contour and the second surface contour each extend from the housing wall to the outflow side of the air-intake means, and the air-guiding element is shaped in such a way that the size of the cross-sectional surface of the outflow space increases continuously crosswise to the outflow direction of the air intake in the outflow direction.

This claims the benefit of German Patent Application DE 10 2010 063525.1, filed Dec. 20, 2010 and hereby incorporated by reference herein.

The invention relates to a handheld power tool, comprising a housingwall and a fan device with an air-intake means and an air outlet in thehousing wall. In particular, the invention relates to a handheld powertool in which an air-guiding element that delimits a diffusor-likeoutflow space is additionally arranged between the housing wall and theair-intake means.

BACKGROUND

The term “handheld power tool” refers, for example, to an electricallyoperated handheld power tool such as a diamond-tipped device, a hammerdrill, a chisel hammer, a screwdriver or a battery-operated drill or thelike.

German patent application DE 103 58 027 A1 discloses that, in order tocool a handheld power tool, cooling air is drawn in by an air-intakemeans through air inlets into the housing of the handheld power tool,and then guided over elements of the handheld power tool that are to becooled such as, for instance, the electric motor and/or the gear, afterwhich it is blown out through air outlets that are likewise located inthe housing.

Such a prior-art handheld power tool is schematically shown in FIG. 1and in FIG. 2.

SUMMARY OF THE INVENTION

It is desirable to ensure adequate cooling of the components of thehandheld power tool that need to be cooled, even in case of a handheldpower tool having a compact design.

It is an object of the present invention to provide a handheld powertool having an air-guiding system with a favorable flow pattern in orderto exhaust the air that has been drawn in by the air-intake means andthat has been warmed up by the heat given off by the components of thehandheld power tool that are to be cooled.

The invention is based on the consideration that the handheld powertools known from the state of the art do not guide the air from theair-intake means to the air outlet, as a result of which the air flowsincorrectly on its way to the air outlet, ultimately preventing thevolume of drawn-in air from flowing quickly over the elements of thehandheld power tool that are to be cooled, and thus detrimentallyaffecting the cooling process.

Therefore, unlike the handheld power tools known from the state of theart, the fan device here additionally has an air-guiding element thatlaterally delimits a diffusor-like outflow space.

With the invention, it has been recognized that the above-mentionedhindrance of the air flow and the associated detrimental effect on thecooling can be due to various reasons. For instance, in the prior-arthandheld power tools, the driving unit and the driven unit are joined toeach other by means of screwed connections. These screwed connectionsare arranged in the space between the housing wall and the fan, which islocated between the driving unit and the driven unit. Especially in thecase of compact models, the screwed connections prevent a fast andsmooth exit of the air from this space. Moreover, such screwedconnections have to be incorporated into a housing that cannot beprovided with air outlets everywhere, for example, because a drill standor a handle is located in the immediate vicinity, or else otherergonomic considerations do not permit the placement of additional airoutlets.

The hindrance of the air flow caused by the screwed connections in theprior-art handheld power tools also occurs when the fan is positionedbetween the handle and the driving unit of a prior-art handheld powertool, since the handle and the driving unit are also joined to eachother by screwed connections, and a fan positioned between the handleand the driving unit is hindered by them when the air is being blownout.

The air flow can also be detrimentally affected by a given design that,for example, does not allow a housing with a round or asymmetricalshape. Moreover, the air outlet might be designed in such a way that itis not adapted to the direction of the air flowing out of the air-intakemeans, and this might cause the air to flow incorrectly.

With the invention, it has also been recognized that, with an eyetowards compensating for the above-mentioned hindrance of the air flow,the solution known from the state of the art, namely, the provision of astronger fan, does not lead to the desired results, since a stronger fanin a compact model only allows a small space between the housing wallwith the air outlet and the air-intake means, so that pressure can buildup in this small space, something which is detrimental to a fast airflow over the components of the machine that are to be cooled,especially since the small space that remains is also already reducedeven more by the above-mentioned screwed connections. Moreover, astronger fan would also entail greater power consumption, which wouldhave a negative effect on the efficiency of the handheld power tool.

In the case of the handheld power tool according to the concept of theinvention, the air-guiding element can delimit a diffusor-like outflowspace between, on the one hand, the housing wall at the air outlet and,on the other hand, an outflow side of the air-intake means, whereby avolume that widens in all three spatial directions and that leads to theair outlet is made available to the air flowing out of the air-intakemeans. This improves the outflow conditions at the air outlet of thehousing, especially in terms of a reduction of flow losses and in termsof pressure recovery. Moreover, the air-guiding element can beconfigured in such a way that the air flowing out of the housing flowsaway from users of the handheld power tool and consequently does notbother them during their work.

Thanks to the improved outflow conditions, the fan device can achieve animproved cooling effect while the power consumption of the air-intakemeans remains the same. Some of the advantages ensuing from this areobvious. For instance, the fan device can be dimensioned smaller and/orcan require less energy, which at the same time translates into a betterenergy balance of the entire handheld power tool.

The air-guiding element can be a passive, single-part or multi-partcomponent that is situated in the space between the housing wall of thehandheld power tool and the air-intake means, the latter usually beingarranged axially and usually blowing air out radially, so that, togetherwith the housing wall and the outflow side of the air-intake means, theair-guiding element delimits an outflow space with a favorable, in otherwords, diffusor-like, flow pattern; this outflow space guides the airthat flows out of the air-intake means and that usually is swirling, tothe air outlet, thereby avoiding flow losses caused by friction and/orincorrect flow patterns.

In other words, thanks to the orientation and shaping of the air-guidingelement, the air can be guided particularly effectively and with afavorable flow pattern. The constant increase in the surface area of thefree cross section, approximately perpendicular to the outflowdirection, offers the possibility of converting kinetic energy of theair flow into useful static pressure. In addition, since the sides ofthe air-guiding element are shaped in such a way that they either faceor face away from the rotational direction of the air-intake means, theair-guiding element—like a distribution blade—deflects the air oppositeto the rotational direction of the air-intake means. This, too, buildsup static pressure and increases the volume flow.

Altogether, the air-guiding element also can combine the advantages of adiffusor with vanes and the advantages of a diffusor without vaneswhich—in spite of a barrier installed in the housing for technical orergonomic measures—allows the air to flow out as it makes a fullrevolution, in other words, by 360°, along the circumference of theair-intake means, without interrupting the air flow from the air-intakemeans.

Within the scope of an especially preferred structural refinement, thefirst surface contour and the second surface contour each extend fromthe housing wall to the outflow side of the air-intake means, therebyleaving a gap between the air-guiding element and the outflow side ofthe air-intake means. The air-guiding element thus makes contact withthe air-intake means, preferably not on the outflow side, but rather, itapproaches it while leaving a gap, and, in terms of the flow, theair-guiding element separates the outflow space from the remaining spacebetween the air-intake means and the housing wall of the handheld powertool. The air-guiding element thus approaches the air-intake means,thereby ensuring that, in terms of the flow, the outflow space isseparated from the remaining space. This type of separation in terms ofthe flow serves to exhaust the drawn-in air with a favorable flowpattern.

For example, as a result of the shape of the air-guiding element, thesize of the cross-sectional surface increases continuously crosswise,preferably perpendicular, to the outflow direction of the air-intakemeans, at least in a partial area of the outflow space.

For instance, the air-guiding element is shaped in such a way that thecross-sectional surface has a first value in a first area that isadjacent to the air-intake means, while it has a second value that isgreater than the first one in a second area that is adjacent to the airoutlet.

Advantageously, the diffusor-like outflow space with the favorable flowpattern can be delimited in that, relative to the outflow space, thefirst surface contour follows a path that is laterally curved outwards.

Advantageously, the diffusor-like outflow space with the favorable flowpattern can be further limited in that, relative to the outflow space,the second surface contour has a curved path with a segment that islaterally curved outwards as well as a segment that is laterally curvedinwards. Here, it is preferable for the second surface contour with thesegment that is laterally curved inwards to extend from the housing wallin the direction of the air-intake means and, towards the air-intakemeans, to make the transition to the segment that is laterally curvedoutwards.

Therefore, the first surface contour can follow a path that is concaveas seen from the outflow space, while the second surface contour, alsoas seen from the outflow space, follows a path that is essentiallyS-shaped, with a convex segment that is adjacent to the housing wall andwith a concave segment that is adjacent to the outflow side of theair-intake means.

In an advantageous manner, these paths of the first and second surfacecontours bring about the above-mentioned enlargement of thecross-sectional surface as the distance from the air-intake meanstowards the outflowing air increases, in other words, in the outflowdirection, and thus they achieve the diffusor effect.

It is also possible to configure the second surface contour with morethan two curves in order to promote a friction-free air guidance.

Within the scope of another especially preferred refinement, theair-guiding element has a first housing extension and a second housingextension that both taper from the housing wall towards the air-intakemeans, especially while also forming an axial edge that liesperpendicular to the outflow direction.

Here, a first side of the first housing extension facing the outflowdirection preferably forms the first surface contour, while a side ofthe second housing extension facing away from the outflow directionforms the second surface contour.

According to this refinement, the air-guiding element consists of atleast two parts and it preferably forms part of the housing of thehandheld power tool. Accordingly, for purposes of delimiting the outflowspace, in a partial area that surrounds the air-intake means, thehousing of the handheld power tool has, on the one hand, the air outletand, on the other hand, the first housing extension facing inwards andthe second housing extension facing inwards.

If the handheld power tool has a part that is proximal to the user, suchas a motor part or a drive part, as well as a part that is distal to theuser, such as a gear part—said parts being joined to each other via afastening means and having the fan device located between them—then, ina refined variant, the air-guiding element of the fan device preferablyphysically surrounds the fastening means, at least on its side facingthe air-intake means. However, the fan device could also be positionedin the handle or somewhere else in the handheld power tool where,together with the air-guiding element, it could physically surround thefastening means.

This prevents air that has been drawn in by the air-intake means fromflowing over the fastening means. Consequently, the air flow is notswirled or hindered, but instead, the air flows over the air-guidingelement that physically surrounds the fastening means.

The fastening means has, for example, a first connection, such asscrewed connections. In this case, the first surface contour preferablypasses the first connection tangentially in the fastening area.

In another especially preferred structural refinement, the first housingextension forms the first surface contour on a side facing the outflowdirection and the second surface contour on a side facing away from theoutflow side, whereby the first surface contour and the second surfacecontour pass the first connection tangentially in the fastening area.Consequently, the air-guiding element covers the fastening means in sucha way that it delimits a first outflow space on one side and a secondoutflow space on the other side.

In accordance with this notion, in another preferred structuralrefinement, the air-guiding element has a third housing extension thattapers from the housing wall towards the air-intake means, while formingan axial edge that lies perpendicular to the outflow direction, andthat, together with the first housing extension and the second housingextension, forms three lateral outflow spaces. Via a number of openingsdistributed along the housing circumference, each outflow space leads tothe outside of the housing of the handheld power tool.

Thus, as a function of the number of connection points between theproximal part and the distal part of the handheld power tool and as afunction of the position and geometry of the openings of the air outletand as a function of the geometry of the air-intake means, in a partialarea that surrounds the air-intake means, the housing preferably forms amulti-component spiral housing having extensions facing inwards thatdelimit a number of diffusor-like outflow spaces with a favorable flowpattern and that guide the drawn-in air in the outflow direction fromthe air-intake means to the appertaining opening. Here, the area of thesecond surface contour curved inwards makes a transition to the areacurved outwards, preferably at approximately the widest place of theconnection in question, which tangentially passes the second surfacecontour.

Preferably, the air-guiding element, for example, in the form of thefirst, second or third housing extension, rises above a barrier. Theterm “barrier” refers to a part of the housing wall that is usuallylocated in the lower section of the housing and that, for structuralreasons, does not have any openings leading to the outside. For purposesof achieving a quick air flow, it is advantageous that the air does notflow over such a barrier, but rather, that the air drawn in by theair-intake means is guided by the air-guiding element past the barrierwith a favorable flow pattern, after which it is guided into an outflowspace having an air outlet.

The air-intake means can be, for example, a radial fan, and theair-guiding element can be a multi-component spiral housing thatsurrounds sections of the radial fan wheel along the circumference witha closed wall, and a radial distance of the closed wall is elevated froman axis of the radial fan wheel along a rotational direction of theradial fan wheel.

According to a preferred structural refinement, the outflow space isadvantageously delimited axially by an air-guiding wall in one directionand by a position-shielding wall in the other direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described on the basis of thedrawing. The drawing does not necessarily depict the embodimentstrue-to-scale, but rather, the drawing is presented in schematic and/orslightly distorted form whenever necessary for the sake of clarity.Regarding additions to the teaching that can be gleaned directly fromthe drawing, reference is hereby made to the pertinent state of the art.In this context, it should be taken into account that a wide array ofmodifications and changes pertaining to the shape and the detail of anembodiment can be made, without deviating from the general idea of theinvention. The features of the invention disclosed in the description,in the drawing as well as in the claims, either on their own or in anydesired combination, can be essential for the refinement of theinvention. Moreover, all combinations of at least two of the featuresdisclosed in the description, in the drawing and/or in the claims fallwithin the scope of the invention. The general idea of the invention isnot limited to the exact shape or details of the preferred embodimentshown and described below, nor is it limited to an object that would berestricted in comparison to the subject matter claimed in the claims.Regarding the dimensional ranges given, values that fall within thecited limits can also be disclosed as limit values and can be employedand claimed as desired. For the sake of simplicity, the same referencenumerals will be used below for identical or similar parts or for partshaving an identical or similar function.

Additional advantages, features and details of the invention ensue fromthe description below of preferred embodiments as well as from thedrawing. This shows the following:

FIG. 1: a longitudinal section of a handheld power tool known from thestate of the art;

FIG. 2: a cross section of a handheld power tool known from the state ofthe art;

FIG. 3: a cross section of the preferred embodiment of a handheld powertool; and

FIG. 4: a longitudinal section of the preferred embodiment of a handheldpower tool.

DETAILED DESCRIPTION

FIG. 1 shows a longitudinal section and FIG. 2 shows a cross section ofa handheld power tool 10 known from the state of the art. The prior-arthandheld power tool 10 has a driving unit 13 and a driven unit 11. Thedriving unit 13 and the driven unit 11 are joined to each other byscrewed connections 19. A radial fan 15 that is also referred to as acentrifugal fan, is arranged between the driving unit 13, that is tosay, the electric motor, and the driven unit 11, that is to say, thegear, of the handheld power tool 10. Between the fan 15 and the housingwall, there is usually a space 17. The air drawn in by the fan 15reaches openings in the housing via this space 17 and then leaves theinterior of the handheld power tool 10 via these openings. Due to abarrier 14 created for technical manufacturing reasons, there is noopening there in the lower section of the housing.

FIG. 3 shows cross section of a handheld power tool 100 according to theconcept of the invention, while FIG. 4 shows the same handheld powertool 100 in a lengthwise section A-A′. Reference will be made below toboth figures.

The handheld power tool 100 has a part 104 that is proximal to a user orholder of the tool 100 and a part 102 that is distal to the user, bothof which are joined to each other by screwed connections 151, 152, 153and 154. The proximal part 104 is normally the driving part with anelectric motor while the distal part 102 is the driven part with thegear. In FIG. 4, these two parts meet at the place marked by a brokenline. The fan device 118 could also be arranged in the handle orelsewhere in the handheld power tool.

The handheld power tool 100 has a fan device 118—some components ofwhich can be seen in FIG. 4 and some in FIG. 3—for purposes of coolingthe driving and/or driven part. The fan device 118 has an air-intake orair-intake means 114 in the form of a radial fan wheel 120 that isarranged axially and that blows approximately in the radial direction.In the housing wall 110 of the handheld power tool 100, there is an airoutlet 116 of the fan device 118 in the form of three openings 121, 122and 123 by means of which the air that is drawn in and blown out by thefan wheel 120 leaves the interior of the handheld power tool 100.

The fan device 118 also has an air guide or air-guiding element 130 inthe form of three housing extensions 131, 132 and 133 that togetherlaterally delimit three outflow spaces 141, 142, and 143, by means ofwhich the air that is drawn in and blown out by the fan wheel 120 isguided with a favorable flow pattern to the appertaining openings 121,122 and 123 of the air outlet 116. The fan device as defined herein thusincludes both rotating and stationary components. The outflow spaces141, 142, and 143 are also delimited axially by an air-guiding wall 126and by a position-shielding wall 128 shown in FIG. 4.

The three housing extensions 131, 132 and 133 each form a first surfacecontour 161 and a second surface contour 162 that extend from thehousing wall 110 to an outflow side 124 of the fan wheel 120. Here, thethree housing extensions 131, 132 and 133 each form an edge, as can beclearly seen. A gap normally remains between the edges of the housingextensions 131, 132, 133 and the outflow side 124, and this gap isnormally dimensioned in such a way that the three outflow spaces 141,142, and 143 are largely separated from each other in terms of the flow.The three edges each form a flow-exposed edge that is approximatelyparallel to the longitudinal axis of the handheld power tool 110 (axialedge).

The outflow direction 127 of the fan wheel 120 or of the air exiting thefan wheel 120 is indicated by the plurality of short arrows on the fanwheel 120. The direction of rotation of the fan wheel 120 is indicatedby the curved arrow.

The first surface contour 161 is shaped in such a way that a tangent ofthe first surface contour 161 on the flow-exposed edge of the firsthousing extension 131 forms an angle α of between 0° and 45° with astraight line that runs through a first screwed connection mid-point151.1 of the first screwed connection 151 and that runs through theflow-exposed edge.

The first surface contour 161 follows a concave path as seen from theoutflow space, and the second surface contour 162, also as seen from theappertaining outflow space, has a segment that is convex close to thehousing wall and a path segment that is concave on the outflow side. Theconcave segments of the surface contours 161, 162 of the first housingextension 131 and of the second housing extension 132 respectively passthe first screwed connection 151 and the second screwed connection 152tangentially. Therefore, the first screwed connection 151 and the secondscrewed connection 152 are surrounded by the first housing extension 131and by the second housing extension 132 respectively, thus causing nodisturbances when the drawn-in air is being exhausted.

The third screwed connection 153 and the fourth screwed connection 154are surrounded by the third housing extension 133, so that theseconnections likewise do not hinder the air guidance. The third housingextension 133 also rises above a barrier 112 which, for structuralreasons, does not have any openings as a rule.

It can be seen in the cross-sectional view according to FIG. 3 and inthe longitudinal view according to FIG. 4 that—starting from the outflowside 124 of the radial fan wheel 120 having a height 125 and towards thehousing wall 110—the three outflow spaces 141, 142 and 143 each widen inall three spatial directions, as a result of which the outflow spaces141, 142 and 143 each form a diffusor that guides the outflowing air tothe appertaining openings 121, 122 and 123 with a favorable flow path.

1. A handheld power tool comprising: a housing wall; and a fan devicehaving an air intake having an outflow side and outflow direction andhaving an air outlet in the housing wall, the fan device having an airguide, the air guide having a first surface contour and a second surfacecontour; the housing wall at the air outlet, and the outflow side of theair intake, delimiting therebetween an outflow space, the outflow spacedelimited laterally by the first surface contour and the second surfacecontour of the air guide, the first surface contour and the secondsurface contour each extending from the housing wall to the outflow sideof the air intake, the air guide shaped in such a way that a size of thecross-sectional surface of the outflow space increases continuouslycrosswise to the outflow direction as a distance from the outflow sidein the outflow direction increases.
 2. The handheld power tool asrecited in claim 1 wherein the first surface contour and the secondsurface contour each extend from the housing wall to the outflow side ofthe air-intake to leave a gap between the air guide and the outflowside.
 3. The handheld power tool as recited in claim 1 wherein the airguide is shaped in such a way the size of the cross-sectional surfaceincreases continuously in a partial area of the outflow space.
 4. Thehandheld power tool as recited in claim 1 wherein the air guide isshaped in such a way that the cross-sectional surface has a first valuein a first area adjacent to the air intake and has a second valuegreater than the first one in a second area adjacent to the air outlet.5. The handheld power tool as recited in claim 1 wherein, relative tothe outflow space, the first surface contour follows a path laterallycurved outwards.
 6. The handheld power tool as recited in claim 1wherein, relative to the outflow space, the second surface contour has acurved path with a segment laterally curved outwards and a furthersegment laterally curved inwards.
 7. The handheld power tool as recitedin claim 6 wherein the further segment extends from the housing wall inthe direction of the air intake and, towards the air intake, to make thetransition to the segment laterally curved outwards.
 8. The handheldpower tool as recited in claim 1 wherein the air guide has a firsthousing extension and a second housing extension that both taper fromthe housing wall towards the air intake.
 9. The handheld power tool asrecited in claim 8 wherein the first housing extension forms an axialedge perpendicular to the outflow direction.
 10. The handheld power toolas recited in claim 8 wherein a first side of the first housingextension facing the outflow direction forms the first surface contour,while a side of the second housing extension facing away from theoutflow direction forms the second surface contour.
 11. The handheldpower tool as recited in claim 1 further comprising a part proximal to auser and a further part distal to the user, the part and further partbeing joined to each other via a fastener, the fan device locatedbetween the part and the further part, the air-guide physicallysurrounding the fastener, at least on a side facing the air intake. 12.The handheld power tool as recited in claim 10 wherein the fastener hasa first connection, the first surface contour passes the firstconnection tangentially in a fastening area.
 13. The handheld power toolas recited in claim 12 wherein the first connection is a screwconnection.
 14. The handheld power tool as recited in claim 12 whereinthe air outlet is configured in the form of a number of openingsdistributed along the housing circumference, the air guide having athird housing extension tapering from the housing wall towards the airintake, while forming an axial edge that lies perpendicular to theoutflow direction, the third housing extension, together with the firsthousing extension and the second housing extension, forming threelateral outflow spaces.
 15. The handheld power tool as recited in claim12 wherein the third housing extension of the air guide rises above abarrier.
 16. The handheld power tool as recited in claim 1 wherein theair intake is a radial fan and the air guide defines a multicomponentspiral housing.
 17. The handheld power tool as recited in claim 1wherein the outflow space is delimited, on the one hand, axially by anair-guiding wall and, on the other hand, by a position-shielding wall.